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Old 24-04-2003, 04:08 PM
Pam
 
Posts: n/a
Default need some soil amendment advice



"Penny S." wrote:

paghat wrote:
Soil ammendment tends to be temporary, & repeat ammendments can
eventually corrupt the soil. Some plants, like camelias, die in soils
that have been ammended two or three times. If one lives in a region
where soils are naturally to the alkaline edge, but wanting a big
collection of rhododendrons, & so truck in acidic topsoil for the
collection, a few years later the soil will have alkalinized to match
the larger environment. I love our naturally acidic soils, but if I
found myself living somewhere to the alkaline side, there'd be a few
things I'd have to give up, but many new things I could grow instead.

Ideally one understands what the natural soils are like in the
region, & if one's immediately accessible gardening areas have soil
in need of restoration or improvement (for instance, because it is
all clay, or some other repairable limitation), it would be ammended
toward the natural state of local soils. That way it might never need
further ammendments ever. Regional soil types are defined by types &
percentages of mineral deposits & topography (such as a valley below
lime-rich hills), types of plants that recycle themselves into soils,
& the rainfall patterns & water tables or amounts of surface water.
One selects plants appropriate to the natural pH levels, finding
plants that do best in the actual local environment.

-paghat the ratgirl


is not adding appropriate organic material (compost etc) also consdired
ameding? I am confused now.

Penny S


As well you might be - I'd be confused after reading that, also :-)) Perhaps
it might be more simply explained:

It is difficult and perhaps impossible to make significant permanent changes
to soil pH - most soils, clay ones in particular, have a buffering ability
which will tend to revert a soil which has been amended to substantially
change pH to an equilibrium level which will be very similar to that of
native, unamended soils. Making significant changes to soil pH also requires
considerable amounts of amendments. It is therefore not generally
recommended that one attempt to significantly alter soil pH but to work
within existing conditions. The good news is that most plants will tolerate
a pretty wide range of soil pH - acid-loving rhododendrons for example are
ideally located in soils with a pH of 5.0 to 5.5 but are perfectly well
adapted to our slightly acidic PNW soils of 6.0 to 6.5. Therefore, unless
you have rather unusual conditions, it is typically unnecessary to make
drastic changes to soil pH, although small adjustments can and are made
frequently - i.e.liming lawns to adjust pH to retard moss development,
adding peat moss to plantings for blueberries, etc.

Amending soils to increase fertility and friability and to improve drainage
is done all the time and is generally considered to be a good idea for
pretty near any soil, specially those which have not been worked in a long
time. This usually involves adding some form of organic material - compost,
leaf mulch, whatever, and/or adding trace elements in the form of rock
powders. The intent is to increase soil porosity and permeability and to
encourage development of soil biota. The only drawback to this is that
overtilling organic matter into the soil (or just plain overtilling) can
destroy soil structure. This is usually more of a concern in agricultural
settings than it is in a residential garden - one doesn't often need to plow
up existing planting areas in residential gardens after initially amending
or improving the soil.:-) And ongoing soil amendment can be accomplished
simply by mulching periodically with a good organic mulch or by topdressing
with compost.

Ideally, soil amending/improvements should be done to an entire planting
area rather than to individual planting holes. Overamending individual
planting holes tends to complicate drainage issues rather than improve them
and discourages plant roots from spreading out into unamended - and to the
plants - less desireable soil conditions. In your circumstance where
wholesale amending is not possible, mulching or topdressing is the way to
go. There are a number of new soil amendments on the market which have been
fortified with both endo- and ecto-mycorrhizae as well as other essential
beneficial soil microbes which will accelarate the decomposition of the root
mass or you can do your own innoculation through the use of aerobic compost
tea. Either way, increasing the populations of benenficial soil
microorganisms will hasten decompostion and result in a very dynamic and
healthy soil condition.

Bottom line - amending the soil in a correct manner is a good thing.
Attempting to significantly adjust soil pH is generally an exercise in
futility and can destroy a rather fragile ecological balance.

HTH
pam - gardengal